Toner for developing electrostatic charge image

ABSTRACT

A toner for developing electrostatic charge images that exhibits superior fixability at low temperature so as to realize satisfactory fixing performance even with less energy, that exhibits high stress resistance so as to be free from blade contamination by molten toner, and that exhibits excellent performances in any environmental conditions. In particular, a toner for developing an electrostatic charge images, comprising at least a binder resin, a colorant and a charge control agent, wherein a low-molecular-weight polymer having functional groups is used at least as the charge control agent and a cycloolefin copolymer resin is used at least as the binder resin.

TECHNICAL FIELD

The present invention relates to toners for developing electrostaticcharge images, which are suitable for image forming apparatuses usingelectrophotographic technologies, such as copying machines, printers,facsimiles, etc., and in particular, relates to toners for developingelectrostatic charge images which are suitable for image formingapparatuses using heat roller fixing systems.

BACKGROUND ART

Dry developers used in the development of image forming apparatusesusing electrophotographic technology may be categorized in thetwo-component developer in which toner and carrier consisting of ferritepowder, iron powder, glass beads, etc., are mixed, the magneticone-component developer in which magnetic powder is contained in thetoner particles, and the nonmagnetic one-component developer which doesnot utilize magnetic force. Toners used in these developers comprisebinder resins and colorants as main components, and waxes for improvinglow-temperature fixability on recording sheets and releasing propertiesfrom fixing rollers, and charge control agents for imparting charge(positive charge or negative charge), etc., are added in addition to themain components. The above materials are mixed at a predetermined ratio,and then the mixture is subjected to processing such as melting andkneading processing, pulverizing processing, classifying processing,etc., so as to produce toner powder, and may then be surface-treatedwith external additives such as silica, titania, alumina, and variousfine resin particles in order to control fluidity, charging property,cleaning property, storage stability of the toner, etc., and a developeris finally provided.

Recently, in the image forming apparatuses as described above,multifunctionalization, speeding up of copying to spread in the boundaryregion between printing machines and copying machines, down sizing, andenergy saving (saving in electric power consumption) primarily forsaving costs, have been desired. According to these desires,simplification and energy saving in fixing systems such as heat rollerfixing systems are required, and the characteristics of the toner whichis adapted to the fixing systems as described above and which is adaptedto speeding up of copying and long life durability of the developer arerequired. Therefore, in the toner, coexistence of two contradictorycharacteristics is required, that is, superior fixability should beobtained even by using small amounts of energy, and stress resistancesuch as resistance to toner melt contamination on a charging blade,etc., should be improved.

In order to satisfy such requirements, styrene-acrylic resin hasprimarily been used as a binder resin for toner up until now. However,in toners containing styrene-acrylic resin, although fixability iseasily improved, and there is a problem of stress resistance reductionthat the toner is easily crushed by friction with sleeves, etc., becausethe strength of the resin itself lowers when the improved fixability isobtained. Thus, polyester resin is widely used in order to make up forthe insufficient stress resistance. However, in the toners containingpolyester resin, charging amount is greatly changed in low-temperatureand low-humidity environments, and the thickness of a toner layer on asleeve is increased with increase of the charging amount, and as aresult, problems of the excessive developing amount and the generationof background fogging occur, and therefore, toners having satisfactoryqualities are not obtained under the present circumstances.

DISCLOSURE OF INVENTION

The present invention was made in order to solve such problems, and itis therefore an object of the present invention to provide a toner fordeveloping electrostatic charge images in which sufficient fixabilitycan be obtained even by small amounts of energy because of superiorlow-temperature fixability, blade contamination by molten toner or thelike does not occur because of high stress resistance, and ability towithstand low-temperature and low-humidity environments is alsosuperior.

A toner for developing electrostatic charge images of the presentinvention comprises at least binder resin, colorant, and charge controlagent, wherein the charge control agent comprises low molecular weightpolymer having functional groups, and the binder resin comprisescycloolefin copolymer resin.

According to the toner for developing electrostatic charge images of thepresent invention, stress resistance and ability to withstandenvironmental conditions are improved by using at least cycloolefincopolymer resin as a binder resin, and superior low-temperaturefixability is demonstrated while retaining sufficient charge by using atleast a low molecular weight polymer having functional groups as acharge control agent. Accordingly even if a large number of sheets iscontinuously copied under environmental conditions such ashigh-temperature and high-humidity or low-temperature and low-humidity,sufficient image density is obtained, and problems such as fogging,blade contamination, generation of offset, etc., are not produced.Furthermore, the low molecular weight polymers having functional groupsalso have effects that non-offset temperature at the lower side of thetoner of the present invention decreases.

In addition, production of cycloolefin copolymer resin, used in thepresent invention as a binder resin, is superior in view ofenvironmental problems, because solvents and endocrine-disruptingchemicals (environmental hormonal substances) used in production ofstyrene-acrylic resins and polyester resins are not used. Furthermore,the toners for developing electrostatic charge images of the presentinvention is extremely superior in view of environmental problems, sincelow molecular weight polymer having functional groups in the presentinvention does not have a structure including metal complexes as is thecase in conventional charge control agents and is a charge control agentof the polymer type which does not contain heavy metals such aschromium, etc.

The toner for developing electrostatic charge images of the presentinvention contains cycloolefin copolymer resin which is a binder resin,low molecular weight polymer having functional groups which is a chargecontrol agent, and colorant, as essential constituent materials, andlow-melting-point wax and other additives, etc., can be appropriatelyadded as necessary in addition to the above essential constituentmaterials. These materials are mixed at a predetermined mixing ratio,and they are subjected to treatments such as melting and kneadingprocessing, pulverizing processing, and classifying processing, so as toform toner particles, and then the toner particles are mixed withexternal additives so that the external additives adhere to the surfaceof the toner particles, and a toner for developing electrostatic chargeimages of the present invention is thereby produced. The toner of thepresent invention obtained in this way can be used as a nonmagneticone-component developer, or as a two-component developer by using acarrier, and in addition, it can be used as a magnetic one-componentdeveloper by containing magnetic powder. In the following, thesepreferable materials will be explained in detail.

The cycloolefin copolymer resin is a polyolefin resin having a cyclicstructure, and for example, it may be a copolymer of an α-olefin such asethylene, propylene, butylenes, etc., and alicyclic compounds havingdouble bonds such as cyclohexene, norbornene, tetracyclo dodecene, etc.,and it may be any random copolymer or block-copolymer. The polyolefinresin having a cyclic structure can be obtained by well-knownpolymerization methods using a metallocene-type or Ziegler-typecatalyst. For example, it can be synthesized by methods described inJapanese Unexamined Patent Application Publication No. 5-339327,Japanese Unexamined Patent Application Publication No. 5-9223, JapaneseUnexamined Patent Application Publication No. 6-271628, etc.

Copolymerization ratio of an α-olefin and a cycloolefin in thecycloolefin copolymer resin can be widely changed by properly settingfeeding mole ratios of both monomers during the reaction so as to obtaindesired resins, and specifically, the mixing ratio of cycloolefin to thetotal of both olefins is set at 2 to 98 mol %, preferably 2.5 to 50 mol%, and more preferably 2.5 to 35 mol %. For example, in the case inwhich ethylene as an α-olefin and norbomene as a cycloolefin arereacted, the glass transition point (Tg) of the cycloolefin copolymerresin which is a reaction product is greatly influenced by the feedingratio of these olefins, and when the feeding ratio of norbornene isincreased, Tg tends to also increase. Specifically, the Tg of producedresin is 60 to 70° C. when the feeding ratio of norbornene is about 60weight %.

In the present invention, it is preferable that the above cycloolefincopolymer resin have at least two peaks in the molecular weightdistribution thereof as measured by gel permeation chromatography(hereafter referred to as “GPC”). The cycloolefin copolymer resin may bea mixture of a low molecular weight fraction and a high molecular weightfraction, or it may be prepared by controlling synthesis conditions sothat the low molecular weight fraction and the high molecule fractionhave at least a peak in the molecular weight distribution measured byGPC, respectively. In addition, number average molecular weight(hereafter referred to as “Mn”) of the low molecular weight fraction isless than 7,500, Mn of the high molecular weight fraction is 7,500 ormore, and the mixing ratio of the high molecular weight fraction ispreferably 5 to 50 weight % in binder resin, and it is more preferably 5to 30 weight %. When the mixing ratio of the high molecular weightfraction exceeds 50 weight %, the degree of uniform kneading isextremely decreased and problems occur in toner performance, andsufficient fixing strength cannot be obtained in low-temperature fixing.In contrast, when it is less than 5 weight %, sufficient non-offsettemperature width cannot be obtained.

Here, “fraction” is defined as each resin component before mixing in thecase in which the cycloolefin copolymer resin consists of a mixture ofresin components having different Mn, and it is defined as resincomponents of portions having each peak divided by a boundary which is alowest point between two peaks in the molecular weight distributionthereof as measured using a GPC method in the case in which thecycloolefin copolymer resin consists of a single resin componentcopolymerized by synthesis.

In the present invention, the cycloolefin copolymer resin containing alow molecular weight fraction of which Mn is less than 7,500 and a highmolecular weight fraction of which Mn is 7,500 or more at the abovemixing ratio is preferably used, and Mn of the low molecular weightfraction is more preferably 1,000 to less than 7,500 and it is mostpreferably 3,000 to less than 7,500, and Mn of the high molecular weightfraction is more preferably 7,500 to 1,000,000, and it is mostpreferably 50,000 to 700,000. In addition, weight average molecular(hereinafter referred to as “Mw”) of the low molecular weight fractionis preferably less than 15,000, and it is more preferably 1,000 to lessthan 15,000, and it is most preferably 4,000 to less than 15,000, and incontrast, Mw of the high molecular weight fraction is preferably 15,000or more, and it is more preferably 100,000 to 1,500,000.

Furthermore, carboxyl groups may be introduced in the cycloolefincopolymer resin in the present invention by a fusing air oxidationmethod or maleic anhydride modification, etc. Compatibility with otherresins and dispersibility of pigments can be thereby improved. Inaddition, similar effects can be obtained by introducing hydroxyl groupsand amino groups using well-known methods. Furthermore, fixability canbe improved by introducing a crosslinked structure by copolymerizingdiene monomers such as norbomadiene, cyclohexadiene, tetracyclododecadiene, etc., in cycloolefin copolymer resin, or by adding a metalsuch as zinc, copper, calcium, etc., to a cycloolefin copolymer resinhaving carboxyl groups.

In the present invention, other resins may be used as the binder resinin addition to the above cycloolefin copolymer resin. In this case, themixing ratio of cycloolefin copolymer resin in the binder resin ispreferably 20 to 100 weight %, and it is more preferably 50 to 100weight %. When cycloolefin copolymer resin is less than 20 weight %,image density cannot be sufficiently maintained under any environmentalconditions in the case of continuously copying of a large number ofsheets, and problems such as fogging and toner dusting tend to occur.

As other resins which can be used in combination with cycloolefincopolymer resin, polystyrene resin, polyacrylic ester resin,styrene-acrylate copolymer resin, styrene-methacrylate copolymer resin,polyvinylchloride, polyvinyl acetate, polyvinylidene chloride, phenolresin, epoxy resin, polyester resin, etc., can be used, and inparticular, in order to improve the fixing performance of the toner, itis preferable that the melting start temperature (softening point)thereof be as low as possible (for example, 120 to 1 50° C.), and inorder to improve the storage stability, it is preferable that the glasstransition point thereof be 65° C. or more.

A charge control agent is added in order to impart charge, and in thetoner of the present invention, it is necessary that the charge controlagent be at least a low molecular weight polymer having the functionalgroup, and the Mn thereof be preferably 1,000 to 10,000, and morepreferably 1,000 to 7,000, and most preferably 1,000 to 5,000. When Mnis less than 1,000, storage stability as a developer is decreased. Inaddition, offset easily occur in fixing. In contrast, when Mn exceeds10,000, compatibility with binder resin is deteriorated, and uniformdispersing is not obtained, and fogging, photo receptor contamination,poor fixing, etc., would be thereby generated. In addition, an effect oflow-temperature fixing is also not obtained.

As such low molecular weight polymers, specifically, for example,positive-charge type styrene-acrylic resins in which quaternary ammoniumsalt type functional groups are added to a main chain as shown in thefollowing chemical formula 1, and negative-charge type styrene-acrylicresins in which sulfonic acid type functional groups are added to a mainchain as shown in chemical formula 2, etc., can be used. Such chargecontrol agents of the polymer type are superior in view of environmentalproblems since they do not have a structure including metal complexeswhich conventional ones have. In addition, in the toner of the presentinvention, well-known common charge control agents can be used incombination with the low molecular weight polymers having functionalgroups, so long as the effects of the present invention are notprevented. Furthermore, the mixing amount of the low molecular weightpolymer in the toner of the present invention is preferably 1 to 15weight parts to binder resin of 100 weight parts, and it is morepreferably 2 to 13 weight parts. When the mixing ratio of the lowmolecular weight polymer is less than 1 weight part, the necessaryelectrostatic charge amount is not obtained, and problems, of thatunevenness of electrostatic charge amount occurs among toner particles,the fixed image is not clear, and photo receptor contamination isincreased, are easily generated. In contrast, when the mixing ratioexceeds 15 weight parts, the electrostatic charge is poor due to reducedability to withstand environmental conditions and compatibility inbinder resins, etc., and fogging is easily generated.

(R₁ represents an alkyl group and R₂ to R₄ represent a hydrogen atom oran alkyl group in the chemical formula.)

(R₁ represents an alkyl group in the chemical formula.)

As a colorant, well-known colorants such as carbon black, aniline blue,chalcoil blue, chrome yellow, ultramarine blue, Dupont oil red,quinoline yellow, methylene blue chloride, phthalocyanine blue,malachite green oxalate, lamp black, rose Bengal, etc., either by thesingle use or by the mixture of two kinds or more, can be used. It isnecessary that the colorant be contained in sufficient amount to formvisible images having sufficient density, and for example, the colorantmay be contained in 1 to 20 weight parts to binder resin of 100 weightparts.

As other additives which may be contained, as necessary, magneticpowders, waxes, etc., can be used.

As a magnetic powder, fine particles such as ferrite powder, magnetitepowder, iron powder, etc., can be used. As a ferrite powder, mixedsintered material of MeO—Fe₂O₃ can be used in the present invention. Inthis case, MeO means oxides such as those of Mn, Zn, Ni, Ba, Co, Cu, Li,Mg, Cr, Ca, V, etc., and one kind or more thereof can be used. Inaddition, as a magnetite powder, mixed sintered material of FeO—Fe₂O₃can be used. It is preferable that the magnetic powder have a particlesize of 0.05 to 3 μm, and it is preferable that the mixing ratio thereofin the toner be 70 weight % or less.

The wax is added in order to improve low-temperature fixability bydecreasing the melting start temperature of the toner, or as a releaseagent, and synthetic waxes, petroleum waxes, etc., can be used. As asynthetic wax, polypropylene wax, Fischer-Tropsch wax, etc., can beused, and as a petroleum wax, paraffin wax, microcrystalline wax,petrolatum, etc., can be used. Furthermore, as other waxes, naturalwaxes such as carnauba wax, rice wax, candelilla wax, etc., can be used.In addition, the above waxes may be used in combination as necessary.

The above materials are mixed at a predetermined ratio, and then themixture is subjected to processing such as melting and kneadingprocessing, pulverizing processing, classifying processing, etc., and,toner particles composing the toner of the present invention can therebybe produced. In addition, the toner particles may be produced bypolymerization methods using raw materials of the above materials.Volume average particle size of the toner particles is generally setwithin 5 to 15 μm.

In the toner of the present invention, it is preferable to adhere anexternal additive thereon in order to control fluidity, chargingproperty, cleaning property, storage stability of the toner, etc. Asexternal additives, silica, alumina, talc, clay, calcium carbonate,magnesium carbonate, titania, magnetic powder, or various fine resinparticles can be used, and in particular, hydrophobic silica ispreferable in the present invention. In addition, many kinds thereof maybe used in combination as necessary. These external additives are addedby post-addition at 0.3 to 3 weight parts to the above toner particlesof 100 weight parts. Furthermore, a surface treatment with the externaladditive can use common mixing machines such as turbine agitaters,Henschel mixers, super mixers, etc.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, effects of the present invention are explained byExamples and Comparative Examples based on the present invention.However, the present invention is not limited by these embodiments.

1. Preparation of Toner for Developing Electrostatic Charge Images

EXAMPLE 1

Cycloolefin Copolymer Resin

-   Ethylene-norbornene copolymer resin A (trade name: TOPAS COC,    produced by Ticona GmbH, Mn: 5,020, Mw: 138,000, Mw/Mn: 27.5, Mn of    low molecular weight fraction: 4,080, Mw thereof: 7,960, Mn of high    molecular weight fraction: 291,300, Mw thereof: 703,400, and high    molecular weight fraction/low molecular weight fraction: 18.5/81.5),    100 weight parts    Charge Control Agent-   Low molecular weight polymer (trade name: FCA- 1001-NS (anionic    type), produced by Fujikura Kasei Co., Ltd., Mn: 3,730, and Mw:    7,970), 5 weight parts-   Polypropylene wax (trade name: Viscol 550P, produced by Sanyo    Chemical Industries Ltd.), 3 weight parts-   Carbon black (trade name: MA-100, produced by Mitsubishi Chemical    Corporation), 7 weight parts

Raw materials in the above component ratio were mixed by a supermixer,were heat-melted and kneaded by a biaxial extruder at a temperature of140° C., were pulverized by a jet mill, and then were classified by adry-type air flow classifier, and toner particles having volume averageparticle size of 9 μm were thereby obtained. Next, hydrophobic silica(trade name: R-972, produced by Nippon Aerosil Co., Ltd.) was added sothat the adhered amount relative to the obtained toner particles was 0.5weight %, and the toner for developing electrostatic charge images ofExample 1 was produced by mixing at a peripheral speed of 40 m/sec for 8minutes using a Henschel mixer.

The above Mn and Mw of the cycloolefin copolymer resin and low molecularweight polymer are values measured by GPC under the followingconditions. That is, the measurement was carried out by flowingtetrahydrofuran (THF) at a flow velocity of 1 ml/min at a columntemperature of 40° C. using polystyrene as a standard, and then themeasured value was converted into a polystyrene equivalent.

EXAMPLE 2

Toner for developing electrostatic charge images of Example 2 wasproduced in the same manner as that of Example 1, except for usingethylene-norbornene copolymer resin B (trade name: TOPAS COC, producedby Ticona GmbH, Mn: 4,250, Mw: 96,100, Mw/Mn: 22.6, Mn of low molecularweight fraction: 3,630, Mw thereof: 6,790, Mn of high molecular weightfraction: 309,100, Mw thereof: 683,800, and high molecular weightfraction/low molecular weight fraction: 12.5/87.5) instead ofcycloolefin copolymer resin A of Example 1. The above Mn and Mw ofcycloolefin copolymer resin are values measured by GPC under the sameconditions as that of Example 1.

EXAMPLE 3

Toner for developing electrostatic charge images of Example 3 wasproduced in the same manner as that of Example 1, except for using 10weight parts of low molecular weight polymer of Example 1.

EXAMPLE 4

Toner for developing electrostatic charge images of Example 4 wasproduced in the same manner as that of Example 1, except for using a lowmolecular weight polymer (trade name: FCA2-01-PS, produced by FujikuraKasei Co., Ltd., cationic type, Mn: 1,560, and Mw: 3,340) instead of thelow molecular weight polymer of Example 1. The above Mn and Mw of lowmolecular weight polymer are values measured by GPC under the sameconditions as that of Example 1.

EXAMPLE 5

Toner for developing electrostatic charge images of Example 5 wasproduced in the same manner as that of Example 4, except for using 10weight parts of the low molecular weight polymer of Example 4.

COMPARATIVE EXAMPLE 1

Toner for developing electrostatic charge images of Comparative Example1 was produced in the same manner as that of Example 1, except for usingpolyester resin (trade name: FC-316, produced by Mitsubishi Rayon Co.,Ltd.) as a binder resin, instead of the cycloolefin copolymer resin A ofExample 1.

COMPARATIVE EXAMPLE 2

Toner for developing electrostatic charge images of Comparative Example2 was produced in the same manner as that of Example 1, except for usingstyrene acrylate copolymer resin (trade name: CPR-100, produced byMitsui Chemicals, Inc.) as a binder resin, instead of the cycloolefincopolymer resin A of Example 1.

COMPARATIVE EXAMPLE 3

Toner for developing electrostatic charge images of Comparative Example3 was produced in the same manner as that of Example 1, except for usinga charge control agent (trade name: T-77, produced by Hodogaya ChemicalCo., Ltd.) instead of the charge control agent of Example 1. This chargecontrol agent is a ferrous complex and is not a low molecular weightpolymer.

COMPARATIVE EXAMPLE 4

Toner for developing electrostatic charge images of Comparative Example4 was produced in the same manner as that of Example 1, except for usinga charge control agent (trade name: TN-105, produced by HodogayaChemical Co., Ltd.) instead of the charge control agent of Example 1.This charge control agent is a molybdic complex and is not a lowmolecular weight polymer.

COMPARATIVE EXAMPLE 5

Toner for developing electrostatic charge images of Comparative Example5 was produced in the same manner as that of Example 1, except for usinga charge control agent (trade name: Bontron N-04, produced by OrientChemical Industries, Ltd.) instead of the charge control agent ofExample 1. This charge control agent is a resin acid modified azinecompound and is not a low molecular weight polymer.

COMPARATIVE EXAMPLE 6

Toner for developing electrostatic charge images of Comparative Example6 was produced in the same manner as that of Example 4, except for usinga polyester resin (trade name: FC-316, produced by Mitsubishi Rayon Co.,Ltd.) as a binder resin, instead of the cycloolefin copolymer resin A ofExample 4.

COMPARATIVE EXAMPLE 7

Toner for developing electrostatic charge images of Comparative Example7 was produced in the same manner as that of Example 4, except for usinga styrene acrylate copolymer resin (trade name: CPR-100, produced byMitsui Chemicals, Inc.) as a binder resin, instead of the cycloolefincopolymer resin A of Example 4.

2. Evaluation of Characteristics

The toners for developing electrostatic charge images of Examples 1 to 3and Comparative Examples 1 to 4 were put into a commercial printer ofthe nonmagnetic one-component development system for using a negativechargeable toner, and the toners for developing electrostatic chargeimages of Examples 4 to 5 and Comparative Examples 5 to 7 were put intoa commercial printer of nonmagnetic one-component development system forusing a positive chargeable toner. An A4 size original having a blackratio of 6% was continuously copied on 10,000 sheets of A4 paper, whilethe above toners decreased by use were replenished, respectively. Thecopying was carried out under different environmental conditions, suchas normal temperature and normal humidity (20° C. and 58% RH),high-temperature and high-humidity (32° C. and 85% RH), andlow-temperature and low-humidity (10° C. and 20% RH). Image density andfogging in a non-image portion in a first sheet under normal temperatureand normal humidity and in the 10,000th sheet under each environmentalcondition were measured, and in addition, existence of bladecontamination by molten toner was observed at the same time. Theseevaluated results are shown in Table 1. TABLE 1 10,000th Sheet 10,000thSheet 10,000th Sheet under normal under high under low temperature andtemperature and temperature and Non-offset First Sheet normal humidityhigh humidity low humidity temperature Image Image Image Image Blade atLower Density Fogging Density Fogging Density Fogging Density FoggingContamination side (° C.) Example 1 1.41 0.83 1.39 0.65 1.39 0.51 1.400.62 ◯ 140 Example 2 1.43 0.52 1.40 0.65 1.38 0.47 1.42 0.59 ◯ 135Example 3 1.40 0.60 1.38 0.48 1.40 0.44 1.41 0.67 ◯ 130 Example 4 1.350.53 1.38 0.62 1.34 0.39 1.36 0.48 ◯ 135 Example 5 1.34 0.50 1.35 0.531.36 0.50 1.37 0.55 ◯ 125 Comparative 1.43 0.53 1.38 0.62 1.29 0.24 1.481.56 ◯ 160 Example 1 Comparative 1.42 0.80 1.40* 0.80* 1.38* 0.61* 1.40*0.55* X 155 Example 2 Comparative 1.41 0.35 1.40 0.45 1.39 0.55 1.410.70 ◯ 150 Example 3 Comparative 1.40 0.62 1.41 0.68 1.38 0.53 1.41 0.65◯ 150 Example 4 Comparative 1.35 0.62 1.36 0.59 1.35 0.39 1.37 0.62 ◯150 Example 5 Comparative 1.36 0.55 1.36 0.49 1.33 0.39 1.44 1.42 ◯ 155Example 6 Comparative 1.34 0.49 1.32* 0.58* 1.38* 0.58* 1.31* 0.49* X155 Example 7

Image density was evaluated by measuring a solid image using areflection density meter (trade name: RD-914, produced by Aretag MacbethLLC.), and fogging was measured by a colorimetry and color-differencemeter (trade name: ZE 2000, produced by Nippon Denshoku Industries Co.,Ltd.). In addition, in connection with the existence of bladecontamination by molten toner, transferred images were examined byvisually, and the existence of stripes due to the blade contamination bymolten toner was confirmed. For toners in which blade cotaminationoccurred, an asterisk is appended after measured values of image densityand fogging in Table 1.

An external fusing unit which can be changed speed and temperature wasproduced by removing only a fusing unit from a commercial copyingmachine (trade name: SF-2035, produced by Sharp Corporation). Then,non-offset temperature at the lower side of each toner for developingelectrostatic charge images of Examples and Comparative Examples wasmeasured at a processing speed of 90 mm/sec using this external fusingunit. These evaluated results are shown in Table 1.

As is apparent from the results in Table 1, in the toners for developingelectrostatic charge images of the Examples 1 to 5 which containcycloolefin copolymer resins and low molecular weight polymers havingfunctional groups, image density and fogging of the first sheet and the10,000th sheet under each environmental condition were within a range inwhich there is no problem in practical use, and in addition, the bladecontamination by molten toner was not at all generated. Additionally,non-offset temperature at the lower side could be drastically reducedparticularly in Example 5. In contrast, in the Comparative Examples 1and 6 using polyester resin instead of cycloolefin copolymer resin,image density was deteriorated under high-temperature and high-humidity,fogging was remarkably generated under low-temperature low-humidity, andfurthermore, non-offset temperature at the lower side was alsoconsiderably high. In addition, in the Comparative Examples 2 and 7using styrene acrylate copolymer resin instead of cycloolefin copolymerresin, blade contamination by molten toner was generated under anycondition, and non-offset temperature at the lower side was also high.Furthermore, in the Comparative Examples 3 to 5 which did not use acharge control agent as specified in the present invention, imagedensity and fogging under each environmental condition were good;however, non-offset temperature at the lower side was still high.

1-6. (canceled)
 7. A toner for developing electrostatic charge images,comprising at least binder resin, colorant, and charge control agent,wherein the charge control agent comprises a low molecular weightpolymer having functional groups, and the binder resin comprisescycloolefin copolymer resin.
 8. A toner for developing electrostaticcharge images according to claim 7, wherein the low molecular weightpolymer having functional groups has a number average molecular weightof 1,000 to 10,000.
 9. A toner for developing electrostatic chargeimages according to claim 7, wherein the low molecular weight polymerhaving functional groups has functional groups of sulfonic acid type orquaternary ammonium salt type.
 10. A toner for developing electrostaticcharge images according to claim 7, wherein the low molecular weightpolymer having functional group is mixed at 1 to 1 5 weight parts to thebinder resin of 100 weight parts.
 11. A toner for developingelectrostatic charge images according to claim 7, wherein thecycloolefin copolymer resin has at least two peaks in molecular weightdistribution measured by gel permeation chromatography.
 12. A toner fordeveloping electrostatic charge images according to claim 7, wherein thecycloolefin copolymer resin comprises high molecular weight fractionhaving number average molecular weight of 7,500 or more at 5 to 50weight % to the binder resin.